Tuberculosis. 125 



through which all the destructive work of tuberculosis is carried 

 on. Where the bacillus tuberculosis lives and multiplies in the 

 animal body these chemical poisons are being constantly formed, 

 and thus its pernicious action is continuous, not only in the seat 

 of the tubercle but through the whole system. 



Tuberculin as a Test. 

 The tuberculin test is based on the fact shown by Koch that it 

 increases the activity of the disease process in tubercle, and affects 

 the whole animal body producing a reaction or rise of tempera- 

 ture in a marked degree. On the ordinary tubercle as seen on the 

 surface, the frequent use of tuberculin produced a more active 

 process of cell growth leading to degeneration and death, so that 

 there was a more speedy transition from the red congested nodule, 

 * through the grayish degeneration into the dead cheesy mass, cut 

 off from all blood circulation. If this dead mass were sloughed 

 off leaving sound tissues to heal, that particular tubercle might be 

 cured. But deeper tubercles usually exist and these are similarly 

 stimulated and their degeneration hastened by the tuberculin ; 

 it is impossible for them to be cast off ; the increasing masses of 

 bacilli, which have been produced under the rapid growth, are 

 shut up in the solid tissues around to furnish new seed for a fresh 

 extension of the disease. As such deep seated tubercles usually 

 do exist with superficial ones, they render tuberculin almost 

 useless as a curative agent, since to eradicate the disease the deep 

 caseated tubercles must be afterward removed by surgical means, 

 a resort which might have been had at the beginning and without 

 the use of tuberculin. 



But this action which renders tuberculin so objectionable as a 

 curative agent makes it of the highest value as a test of tubercu- 

 losis in animals. The minute dose which has no effect on a 

 healthy cow, horse or pig, when employed on the slightly tuber- 

 culous one produces an acceleration of ■ the disease process and 

 in eight to fifteen hours a material rise of temperature. This has 

 been now employed on thousands of cows and those who have 

 used it most, value it the most highly, whereas many who at first 

 reported reactions in non-tuberculous animals are now acknow- 

 ledging with Nocard that the fBult has been mainly their own, for 

 small tubercles were present but were overlooked through their 

 ailure to examine the bones and other organs. 



